The students of Robert Mellette, a science teacher in Connecticut, call him "space man."

After John Cazanas, an English teacher, was nominated to be a teacher in space, he received a congratulatory post card addressed, simply, "Buck Rogers, Rockford, Iowa."

David Zahren's students in Prince George's County are proud of him. "On the last day of school," he said, "I got a binder with a space shuttle on the cover and a photo of me and inside were 600 letters from everyone in the school saying how proud they are of me.

"You automatically become a folk hero."

These three, along with 111 elementary and secondary school teachers from across the country and the three U.S. territories, are here for a week of workshops and interviews because they were nominated by the National Aeronautics and Space Administration to participate in the Teacher in Space Project, announced last August by President Reagan. They were selected from 10,690 applications; 10 semifinalists will be announced Monday. The winner is scheduled to lift off Jan. 22, 1986.

They gathered yesterday in the Dirksen Senate Office Building to meet members of Congress, nibble vegetables and cheese and bask in the limelight. They met the first astronaut to be elected to Congress, Sen. John Glenn (D-Ohio), and they heard from the first member of Congress to ride the space shuttle, Sen. Jake Garn (R-Utah): "I can't tell you how excited I am to be here just knowing that one of you is going to get to fly."

Said Alan Ladwig, manager of the Space Flight Participant program, "We're looking for someone who can really feel this whole experience in their heart and soul and come back and share it with the American people."

He said the laborious application process is more than a "PR stunt," adding that the large numbers of teachers involved in the selection process have brought the space program and the teachers themselves into the public eye.

Program managers also hope the publicity encourages more students to excel in science and math. Said Zahren, who chairs the science department at G. Gardner Shugart Middle School in Hillcrest Heights, "I don't know of any that I've taught that's gone on to be a teacher, and that worries me."

The teachers say all the attention has made them philosophic rather than competitive.

"None of us are losers. Some will just be bigger winners," said Kathleen Beres of Baltimore, whose students sent a flower to her home and decorated the Kenwood High School lobby with a banner when her selection was announced.

Ronald Reynolds of Barrington, R.I., said he was "in the depths of despair" about being a teacher four years ago, but now feels enthusiastic. "Even if I don't get in, I still feel quite good about it," he said.

So far, the teachers have met three astronauts and attended numerous workshops on the shuttle and space technology. Equipped with videotapes, slides, films and booklets, they have been asked to serve as "ambassadors" for NASA in their home states.

The countdown for the semifinalists is scheduled to end in September, when the winner and a backup candidate are named. According to Ladwig, criteria will include originality, ability to communicate, community involvement and commitment to teaching. Each will receive 120 hours of training before the launch.

Said Zahren, "They're treating us as if we're astronauts already."

Nancy Cooksy, a biology teacher at Eastern High School here, said, "I think the most exciting thing has been meeting the other teachers," as friends and as resources for her teaching.

Cooksy said students have been touched by the honor she has received. She was hesitant, though, to predict that more would continue their math and science studies as a result. "They have received a sense of education being important and a sense of themselves being important, which they need."

But some of her students may not have paid strict attention to the details. When Cooksy asked some why they weren't in class, she said they replied, "I thought you were going to the moon."